Heard about a quicky technique for detecting TdT in leukemias using whole blood lysis during the recent ASCP teleconference question & answer period on Wednesday. Check it out, or are some of you using this technique already? Let us know! Set up your leuk panel (note: we run TdT as secondary testing, so it is not on our initial leuk panel). After lysing / acquisition / analysis, choose any tube that did not stain with a FITC-conjugated marker (maybe your pesky isotype control tube?). Toss in some TdT-FITC. Incubate 20 min, wash and re-aquire. Hmmm... According to the presenter, "the cells have already been lysed / fixed with a commercial reagent and the cell membrane has been permeabilized." I was skeptical but had to try it. Being a QC freak, though, I set up a matched isotype control and a TdT tube for each specimen as follows: QS the leftovers from a FITC and PE negative tube to 200ul. Divide this between two fresh tubes. Add Ig-FITC (isotype) to one tube; add TdT-FITC to the other tube. Add CD19-PE to both tubes. Incubate 20 min RT, in the dark. Wash twice. Run with it. I happened to have a pediatric B-ALL and an adult AML in my done rack that week. The B-ALL TdT was also run as usual using a commercial Fix & Perm reagent. The B-ALL was CD19-PE postive, TdT positive with both techniques; the AML was CD19-PE and TdT negative with this quickie technique (Fix & perm TdT not performed). I haven't done a literature search yet; that's next. And lots of parallels... Cathy Fritschi Sentara Norfolk Gen. Hosp. Norfolk, VA
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